Process of producing tetra-alkyl lead



Fatented- Mar, 6, 1928.

MNNEE'E P. MONR'UIE, 9F PENNS GRUVE, NEW JERSEY, AND KI WILLIAMS, O13 @Llll) HIGZKQRY, TENNESSEE, AS$IGNORS T0 .E. I. lDU PUNT DE NEMOURS do GOMEANY, t illlbl lllldtil'i'tllll', IDELAWARE, A GORPORrhTION 0F DELAWARE.

PRUGESS Q35 PRODUCING TETM-ALKYL LEAD.

g pies of substances which will react wi secure with formation of nascent hyen, and these substances can be used to ce1'.' extent alternatively. The present inv i' however, is concerned with the use 0 hydroizylic mixture in which the alcohol predominates.

The synthesis of lead tetra-allryls from lead sodium alloy and alkyl halide probably occurs in steps which may be represented by the following equations:

ll) Pb +XAll-r Hlg --r Pbllllr hllg t l) l latllt Hl-llc; --rlilalrllg-t n arse/tn armada-ere This theory of the reaction is founded in part upon the observations that as the reactants are rigorously purified and the con ct watenalcohol or other dissolved hydrozylic compound a preaches zero as a limit, the yield out ead tetra-alkyl approaches Zero as a limit also. Uri the other hand the presence of an excessive amount of alcohol, water or other dissolved hydroxylic compound is undesirable inasmuch as undue side reaction (for example, the evolution of hydrogen) follows, with corresponding loss.

lt is therefore advantageous to control the violence of the side reaction. To accomlish this the alcohol content may be adyusted to the exigencies of the manufacturing program as disclosed in co-pending applications, or the violence of the side reaction may be mitigated by suitable dilution of the hydronylic compound. lln the case of water such dilution may be efi'ected, as has already been pointed out in a co-pending appl1catiomby dissolving therein a salt,

application filed llctober it, 13%. serial lto. 62,594.

it has now been ascertained, when the process is carried out with hydroxylic come to pound composed largely of alcohol, that it is advantageous to control the reaction by the gradual addition of a concentrated al coholic solution. of potassium hydroxide. This solution consisting 01 an equilibrium co mixture of alcohol, water, potassium ethylate and potassium hydroxide is readily miscible with the alkyl halide and in this respect possesses an important advantage when the reaction is carried out on a large scale. To this property we ascribe tentatively, the fact that excellent yields of lead allryl are ob tained by the use of alcoholic potash even when no other catalytic agent of the type used in the Grignard synthesis is present,

Catalysts of this type which are especially suitable for use in this process are substances containing a tertiary basic nitrogen atom, for example, dimethylaniline, diethylaniline, pyridine, triethylamine, etc.

The following example is furnished as an illustration of our process only, and it is not our intention to limit ourselves to the proportions, temperatures, particular substances or other details therein indicated.,

Example.

till

183 grams of lead-sodium alloy contain ing 16% sodium was added to a mixture of 250 cc. ethyl bromide, 10 cc. pyridine and 2.5 cc. 2B alcohol, contained in a l liter round flask fitted with a reflux condenser. The flask was immersed in a thermostat maintained at 40-45" C. and cc. concen trated alcoholic potassium hydroxide solu to tion added every 15 minutes, with vigorous shaking, for 16 hours. The excess ethyl bromide and lead tetra-ethyl were then separated by steam distillation.

In place of ethyl bromide we may use, for no example, ethyl chloride. Where the product desired is some other lead-tetra alkyl than the ethyl alkyl, the corresponding alkyl halide should be employed. It is obvious that other concentrated alcoholic alkalies we may be substituted for the alcoholic potash although it may be noted that among such that are commercially available, potassium hydroxide has the unique advantage of high basicity and high solubility in alcohol, rot Other variations from the process as illustrated, which are obvious to a chemist skilled in the art may be made without departing from the invention.

As has been noted in other co-pending applications, there is formed, in addition to lead tetra-ethyl, an appreciable amount of heXa-ethyl-di-plumbane when the process is carried out according to the specifications of this application. This may, however, be converted to lead tetra-ethyl by known methods.

We claim:

1. A process for the manufacture of tetraalkyl lead from lead alloyed with a monovalent element capable of liberating hydrogen from alcohol which comprises treating such alloy with an alkyl halide and an alcoholic solution of potassium hydroxide.

2. The process of producing tetra-alkyl lead which comprises effecting a reaction between a lead-sodium alloy, an alkyl halide and a hydroxylic compound, in which process the hydroxylic compound comprises an alcoholic solution of an alkali.

3. In the process of producing tetra-alkyl lead which comprises effecting a reaction between an alloy. of lead containing a monovalent element capable of liberatinrr hydrogen from alcohol and an alkyl ha ide, the step of adding an alcoholic solution of an alkali.

4. The process of making a lead ethyl which comprises reacting a lead-sodium al- 10y with an ethylating agent in the presence of an alcoholic solution of an alkali.

5. The process in claim 4 in which the ethylating agent is an alkyl halide.

6. The process of producing tetra-alkyl lead which comprises treating an alloy of lead comprising a highly electro-positive metal un er reaction conditions with an alkylatmg agent in the presence of an alcohohc solution of a caustic alkali.

7. The process of making a lead ethyl which comprises reacting a lead-sodium alloy with an ethyl halide in the presence of an alcoholic solution of an alkali.

8. The process of making tetra-ethyl lead which comprises reacting a lead-sodium alloy of the formula PbNa with an ethyl halide in the presence of an alcoholic solution of potassium hydroxide.

9. The process as set forth in claim 8 in which the ethyl halide is ethyl bromide.

10. The process of producing tetra-ethyl lead which comprises treating lead alloyed with a monovalent element capable of liberating hydrogen from water under reaction conditions with an ethyl halide in the presence of an alcoholic solution of an alkali.

11. In the production of tetra-alkyl lead from an alloy of the formula PbNa an alkyl halide and alcohol, the process of effecting control of the reaction between the sodium and the alcohol which comprises adding the alcohol as a concentrated alcoholic solution of an alkali.

12. The process of making a lead ethyl which comprises reacting a lead-sodium alloy with an ethylating agent in the presence of an alcoholic solution of an alkali and a substance containing a tertiar basic nitrogen atom, said substance being adapted to catalyze the reaction.

13. The process as set forth in claim 12, in which the substance containing a tertiary basic nitrogen atom is pyridine.

14. The process as set forth in claim 11, in which the alcoholic solution of an alkali is added in small batches at substantially regular intervals until the reaction is com pleted.

In testimony whereof we afiix our signatures.

KENNETH P. MONROE. KI WILLIAMS. 

